The present invention relates to a circuit arrangement for determining the load current in a reversible d-c controller or chopper having a bridge circuit connected across a supply voltage source, the bridge circuit comprising four bridge arms, each of which includes an antiparallel circuit comprising an electronic switch and a bypass diode, the bridge circuit further including a measuring sensor provided in two of the bridge arms.
Such a circuit arrangement is known, for instance, from the journal "Elektrie" 28 (1974), pages 368 to 370. In the known circuit arrangement resistors are provided as measuring sensors in the two bridge arms which are connected to the bus at reference potential. Although this circuit arrangement allows the load current to be determined at zero potential, elaborate and expensive electronic circuitry is required for its evaluation. An object of the invention is to provide a circuit arrangement of the type mentioned above by which the load current can be determined in a relatively simple and convenient manner. A further object is to provide such a circuit arrangement in which the load current is determined at zero potential, that is, in a circuit isolated from the d-c supply buss.